Hello I have 1998 Jeep cherokee xj 4.0 I6.

Ever since summer 2019 my Jeep will 8/10 times lag and sputter when I startup. I checked and this happens in neutral too, because initially I thought the trans might be slipping. I found that the problem goes away after 5 sec -1 min after it starts, then the car runs perfectly fine. Also the problem seems to go away faster if I floor the gas pedal. Sometimes I can hear a popping noise coming from beneath the car when the problem acts up harder.

This all seems to point to the fuel pump, oxygen sensor, or the fuel injectors - at least to my understanding of it.

Can anyone tell me if I’m on the right track or what they think it is?

-So far I have replaced the cap, rotor, spark plugs, spark plug wire, and air filter-

Thank You for any and all advice!!

 

Get the codes from the Jeep, then you'll know if it's a sensor issue. Get hold of a fuel pressure gauge and attach it to the schraeder valve on the fuel rail.
Fuel injectors are harder to test but usually pretty reliable.

 

Ok I got it scanned and threw no codes. Guy at the autozone said something about it only sending 1 misfire report and 3 were needed for a check engine light which would provide a specific code.